He is 5ft 8ins (1.76m), weighs ten stone (63.5kg) and wears an extra large uniform.

Not unusual for a teenager going through a growth spurt, perhaps, but his appearance triggered suspicions that schoolboy Prince Summerfield might be an adult leading a double life.

Today, those suspicions were laid to rest as the headteacher of the 14-year-old's school admitted that he had made a mistake by excluding him because he thought the boy was actually 24.

Prince, whose family moved to Britain from Malawi, was sent home from the Petersfield school in Hampshire at the start of this term after the head, Nigel Poole, questioned his age.

The school said last week that it was attempting to "clarify aspects of this young man's background", and explained that the vigilance was necessary to comply with its child safeguarding policy.

His parents David and Ennettie – who said that if her son was 24, she would have to have given birth aged five – produced evidence including his Malawian birth certificate, which shows that he was born on 24 September, 1996.

A school spokeswoman said: "Following extensive checks with the relevant authorities, the Summerfield family have been able to prove with complete authenticity that Prince is 14 and should be at secondary school.

"Mr Poole has now contacted the family to admit his mistake and apologise for the upset caused.

"He has invited Prince back with immediate effect and promised to ensure his smooth re-integration."

Poole said: "I am sorry for the upset this episode has caused.

"I am now satisfied that all necessary checks confirm Prince is actually 14 and am happy to welcome him back to TPS."

The school has a specialism in the performing arts and is rated outstanding by Ofsted. In its statement last week, it emphasised that it was a "highly successful and inclusive" school, which sought to do the best for every pupil who joined. "This young man would be no exception," the school said.

While most people consider one education enough, there is at least one example of an adult masquerading as a schoolboy. In 1994, a 32-year-old man spent a year at a school in Scotland posing as a 17-year-old pupil.

The man, who called himself Brandon Lee, enrolled at Bearsden Academy in Glasgow two decades after he attended the school as a boy. Education officials said he had fooled both teachers and pupils.

His deception came to light after a dispute on holiday in Spain, which led to Spanish police discovering two passports, one indicating that he was a teenager and the other giving his age as 32.